How to build a PHP form Dynamically with OOP?

Question

How would I go about creating a real world form creation class that I can use to display a new form with fields of different types, as how many fields I want, I can use drop downs and I can do all of this by using OOP?

Answer 1

You definitely should use OO PHP to do forms, and all the rest of your HTML output. I could not find any PHP library (many of the links in these answers are dead) to do what I wanted, so I wrote PHPFUI. It is not a generic HMTL output library, but outputs pages for the Foundation CSS Framework. You could easily use the same technique to output a more vanilla page, or Bootstrap or what ever. I did not want to write a generic HTML OO PHP library, as I wanted something lean and mean for performance reasons. Also I don't like to over engineer stuff, so it is hard coded to Foundation. But the same principles would apply to any PHP library that would want to output clean HTML with no validation issues, which you often find in hand written HTML.

Answer 2

I will go against other advice here and suggest that you build your own library to generate forms. If you fail, you will still learn a lot in the process.

The design process is most important here. You start from the top and ask yourself what goes on a form. At an abstract level, a form is full of elements. Some are visible, some are not, some can be entered by the user but others cannot, some elements can trigger other elements... and the list goes on...

Eventually you end up with elements that are "decorative" (Text, Headings, Separators, Fieldsets, Links, Images), elements that are interactive (Inputs, Dropdowns, Checkboxes, Radio buttons, Submit Buttons) and finally elements that are neither decorative nor interactive (Hidden Inputs, Anchors and elements that act as containers to group other elements.)

Once you have the different categories organised you start looking into features that all elements have and you can put that into the base element class. Then you go up the chain making your classes doing more and more, inheriting from other simpler element classes. In my library, the base element class is called form_element and each form_element has a unique name that no other element within the same form can have. A form_element also has a set of attributes. It has a function that all elements have called render(). In the base class render() does nothing (so a base element is always invisible) but in derived classes it starts producing HTML. By the way, I never make any of my classes create HTML. Instead I have a static class called html which writes HTML for all the classes that needs its services.

Very early in the chain of form elements, you should have one, a container that groups others. It should have an add() function and its render() function should consist of calling the render() function of all its sub-elements. the form class will be derived from this container class.

Spend plenty of time on the design. Pay attention to compatibility with the rest of your library.

If you want the data from the form to come from a database and be saved to one, you will need to add this functionality and have a form element class linked to a table and column. Here too, I have a separate DB class that can retrieve/save the data. I have a query class that creates queries. Form elements should have nothing to do with creating HTML, creating queries or accessing a database. My static class DB and my query class take care of the dirty work. The form class should only be involved with form stuff. The form class collects into an array all the tables and columns for the fields that need to be saved and pas it to the query class which creates the query which is then passed to the DB class which executes it.

Once you are properly setup, what appears to be horrendously complicated suddenly becomes very easy with properly designed classes.

Because you have a class that can write HTML, your form class needs to just html::init() and follow it with render() and the entire HTML code for the form is available within the html buffer. html::output() flushes everything out.

Validation is also handled externally with a static validation class. Form elements that can be validated hold validation instructions within an array in a format that can be passed directly to the validation class. Each element that needs to be validated is bound to an error element which displays the error if the element does not validate or remains invisible if all goes well.

This is to show you that when you design a form environment (or anything else) you really need to consider absolutely everything before you get started. The work that you put into it may not immediately translate into code that can power your application but it will sure make you a much better developer, thus making your future projects much easier to handle.

The form class creates a form, the html class creates the HTML, the query class makes queries and the DB class handles the database. If your classes start doing work that should be done by separate classes, you have a design problem.

Here is a code sample to show how my form library works:

$fm = new form('myform');
$fm->binding(FORM_DATABASE);
$fm->state(FORM_RETRIEVE); 
$fm->set_recno(1);
$fm->add(new form_heading("My form"));
$fm->add($el=new form_input("name",40));
$el->bind_data('mytable','mycolumn');
$el->set_attribute('size', 25);
$el->set_default('Name');
$fm->add($el=new form_submit("submit_btn","Submit"));
if($fm->manage())
 {
 redirect or do something else here. The interaction with the form is done. The initial state for the form was FORM_RETRIEVE. If it had been FORM_NEW it would have displayed default values instead of the retrieved record and saved the form as a new record in the table. 
 }

Note that the manage() function of the form takes care of absolutely everything, retrieving data from the database, rendering the form into the view, validating data and saving it back to the database.

One of the advantages of creating forms programmatically (as above) is the option to write your own form-based code generator to create the code to make your forms.

I hope this can help you or someone else.

Answer 3

Just for reference, Object Oriented Forms by Khurram Khan is an excellent OO forms implementation for PHP.

Here is a sample of what the code looks like:

$form = new Form("Register", "form.php"); 

$personal = new Block("Personal Information"); 

$name = new Text("name", "Your name"); 
$name->setDescription("this is my description"); 
$name->addValidator(new MaxLengthValidator("The name you have entered is too long", 30)); 

...

Another more popular implementation is PHPlib. However, I find this to be a bit clunky; it seems like it's just some standard functional programming wrapped in a class.

Another option would be writing an abstraction for the built in DOM library. This will allow you to manually create any kind of form and form element using OO notation, with the added benefit that you will be returned an OO DOM instance that can be used elsewhere in your program.

Answer 4

To be honest I wouldn't roll my own, considering there are a few mature form packages out there for PHP.

I use PEAR's HTML_QuickForm package (http://pear.php.net/manual/en/package.html.html-quickform.php) for PHP4 sites.

For PHP5, I'd have a look into Zend_Form (http://framework.zend.com/manual/en/zend.form.html).

For my quickform code, I use a helper class that lets me define forms using a config array. For example:

echo QuickFormHelper::renderFromConfig(array(
  'name' => 'area_edit',
  'elements' => array(
    'area_id'           => array('type' => 'hidden'),
    'active'            => array('type' => 'toggle'),
    'site_name'         => array('type' => 'text'),
    'base_url'          => array('type' => 'text'),
    'email'             => array('type' => 'text'),
    'email_admin'       => array('type' => 'text'),
    'email_financial'   => array('type' => 'text'),
    'cron_enabled'      => array('type' => 'toggle'),
    'address'           => array('type' => 'address'),
  ),
  'groups' => array(
    'Basic Details'   => array('site_name', 'base_url'),
    'Address Details' => array('address'),
    'Misc Details'    => array(), // SM: Display the rest with this heading.
  ),
  'defaults' => $site,
  'callback_on_success' => array(
    'object' => $module,
    'function' => 'saveSite',
   ),
));

Note that the above element types 'address' and 'toggle' are in fact multiple form fields (basically, meta-types). This is what I love about this helper class - I can define a standard group of fields with their rules (such as address, credit_card, etc) and they can be used on lots of pages in a consistent fashion.

Answer 5

You definitely can. Consider a Form class which stores information about the form itself: the method, action, enctype attributes. Also throw in stuff like an optional heading and/or description text at the top. Of course you will also need an array of input elements. These could probably be put into their own class (though subclassing them for InputText, InputCheckbox, InputRadio maybe be a bit over the top). Here's a vague skeleton design:

class Form {
    var $attributes,    // array, with keys ['method' => 'post', 'action' => 'mypage.php'...]
        $heading,
        $description,
        $inputs        // array of FormInput elements
    ;

    function render() {
        $output = "<form " . /* insert attributes here */ ">"
              . "<h1>" . $this->heading . "</h1>"
              . "<p>" . $this->description . "</p>"
        ;
        // wrap your inputs in whatever output style you prefer:
        // ordered list, table, etc.
        foreach ($this->inputs as $input) {
            $output .= $input->render();
        }
        $output .= "</form>";
        return $output;
    }
}

The FormInput class would just need to store the basics, such as type, name, value, label. If you wanted to get tricky then you could apply validation rules which would then be converted to Javascript when rendering.